The real action begins when Gerakines hits the ice with radiation.
Earlier studies by other researchers have looked at ice chemistry using ultraviolet light. Gerakines opts instead to look at cosmic radiation, which can reach ice hidden below the surface of a planet or moon. To mimic this radiation, he uses a proton beam from the high-voltage particle accelerator, which resides in an underground room lined with immense concrete walls for safety.
With the proton beam, a million years' worth of damage can be reproduced in just half an hour. And by adjusting the radiation dose, Gerakines can treat the ice as if it were lying exposed or buried at different depths of soil in comets or icy moons and planets.
He tests the three kinds of water-plus-amino-acid ice and compares them to ice made from amino acids only. Between blasts, he checks the samples using a "molecular fingerprinting" technique called spectroscopy to see if the amino acids are breaking down and chemical by-products are forming.
As expected, more and more of the amino acids break down as the radiation dose adds up. But Gerakines notices that the amino acids last longer if the ice includes water than if they are left on their own. This is odd, because when water breaks down, one of the fragments it leaves behind is hydroxyl (OH), a chemical well-known for attacking other compounds.
The spectroscopy confirms that some OH is being produced. But overall, says Gerakines, "the water is essentially acting like a radiation shield, probably absorbing a lot of the energy, the same way a layer of rock or soil would."
When he repeats the experiments at two higher temperatures, he is surprised to find the acids fare even better. From these preliminary measure
|Contact: Liz Zubritsky|
NASA/Goddard Space Flight Center